Have you tried following the steps in the
Ground Control Pro manual, starting on page 18?
Just a quick clarification, but in your message you write that you want to control the presets with the bank up/down buttons. The way I'd set your config up, since you have traditional pedals in the loop, is with the 4 presets per bank with 8 instant access switches to toggle the loops of your 6 stompboxes. When you use bank up and down, you won't be sending program changes to the PSA, you'll be readying a new set of 4 presets (program changes) to send to the PSA. This mode is on page 17 of the manual.
Maybe if you can try working through the manual's instructions, and let us know exactly where you're stuck, we can help more, but both manuals look quite complete to me (the PSA MIDI mapping section is on page 17 of
its manual) and I think all the information is there to make this work.
Nice choices in gear, by the way. I like your style!